The long-term goals of this project are to investigate demineralization of enamel under intraoral conditions, and to examine the factors that can affect these processes. Recent studies have shown that calcium lactate (CL) can be effective in reducing intraoral demineralization when incorporated into solid food. CL appeared to be most effective when high concentrations of calcium accumulated in the plaque during periods of active acidogenesis. Experiments are proposed to determine conditions that will favor the accumulation and maintenance of high calcium concentrations in plaque, and to monitor the effects of such conditions on enamel demineralization. Experiments will be carried forward in three major areas, (1) the incorporation of CL into foods that differ in texture and retentiveness such as doughnuts, sponge cake, chocolate, creme sandwich cookies, and cookies made with different shortenings; (2) the role of plaques with different diffusion properties, such as streptococcal plaque with low or high glucan content, or natural plaque; and (3) the use of calcium salts with different solubilities, such as calcium acetate, chloride, gluconate, glycerophosphate and levulinate, that may release calcium more or less rapidly into the plaque. The intraoral delta Ip system will be used in these studies. In this system blocks of bovine enamel will be covered with streptococcal plaque and exposed to intraoral conditions. Demineralization will be determined as changes in enamel porosity. In addition, determinations will be made of plaque acidity and calcium content. In parallel experiments, analyses will be made of the calcium contents of food particles that become entrapped on the natural dentition as a way of assessing the effectiveness of supplemented foods to deliver calcium to the natural plaque in situ. The results should increase our understanding of the mechanisms by which soluble calcium salts reduce enamel demineralization intraorally. They should also provide a sound basis for the modification of existing foods or the development of new products with reduced cariogenic potential.